Optimization of radiographic parameters for paediatric cardiac angiography.

In the paediatric cardiac catheterization laboratory the reduction of the radiation dose of diagnostic and interventional procedures is of high priority. Therefore, we performed an experimental study for optimizing the automatic exposure control (AEC) for cardiac angiography. With a Philips Integris BH 5000 system, six AEC programs were configured to acquire X-ray images of 8 cm to 18.5 cm thick PMMA phantoms at tube voltages between 50 kV and 90 kV, with 0.2 mm or 0.4 mm Cu filters and with or without an anti-scatter grid. At constant detector dose, entrance dose (ED) and image quality were evaluated as functions of the voltage. Changes in image quality were determined by the differential signal-to-noise ratio measured within regions of low (SNRb) and high (SNRd) attenuation. At equal voltages, ED saving was approximately 29% with the 0.4 mm Cu beam filtering as compared with 0.2 mm Cu, largely independent of object thickness. SNRb and SNRd were only dependent on the voltage. While SNRb was high at low voltages, SNRd showed a maximum at approximately 79 kV. Using a grid, ED increased with increasing object thickness by a factor of 1.9 to 3.5. At equal voltages, the grid led to significant image improvements, with SNRb and SNRd increasing by 27% and 11%, respectively. SNRb and SNRd are useful descriptors of the image quality in cardiac angiography. Highest image quality was found with tube voltages between 55 kV and 77 kV, independently of object thickness. To minimize dose, the thickness of the copper filter should be chosen to be as large as possible provided the tube's power limit allows keeping the voltage below the upper limit. In view of the substantial image improvement, the use of a grid is recommended for all patients, even for newborns.

First-pass nuclear angiocardiography in the evaluation of patent ductus arteriosus in dogs.

First-pass nuclear angiocardiography (FPNA) was performed in 5 normal dogs and in 19 dogs with left-to-right shunting patent ductus arteriosus (PDA). Affected dogs were evaluated before and after an occlusion procedure (surgical ligation or transarterial coil embolization). Two methods of analysis were used to evaluate the pulmonary time-activity curves and assess the magnitude of the shunt. One method involved the calculation of a simple count ratio (C2:C1). The other method used gamma variate modeling to estimate the ratio of pulmonary to systemic blood flow (QP:QS). Values for normal dogs (mean +/- SD) were C2:C1 = 0.39 +/- 0.11 and QP:QS = 1.10 +/- 0.03. Values for affected dogs were C2:C1 = 0.59 +/- 0.17, QP:QS = 2.01 +/- 0.46 before intervention and QP:QS = 1.21 +/- 0.17, C2:C1 = 0.42 +/- 0.12 after intervention. Both methods detected significant differences between normal and affected dogs (QP:QS, t-test, P < .001; C2:C1; t-test; P = .018) and between affected dogs pre- and postocclusion (QP:QS. paired t-test, P < .001; C2:C1, paired t-test, P = .002). However, QP:QS was a better separator of normal from affected animals. First-pass nuclear angiocardiography, by the gamma variate method, may be a useful, adjunct diagnostic test in evaluation of animals with left-to-fight shunting PDA, particularly in animals with residual shunting after an occlusion procedure.

[Comparative study of post-infarction myocardial viability after fibrinolysis by stress tomoscintigraphy and echography: can viability be detected without ischemia?]. / Etude comparée de la viabilité du myocarde en post-infarctus après fibrinolyse par tomoscintigraphie et échographie de stress: peut-on détecter la viabilité sans l'ischémie?

The objectives of this prospective study was to define the comparative ability of stress myocardial scintigraphy and dobutamine stress echocardiography to demonstrate post-MI myocardial viability, assessed on the functional recovery in terms of improvement of global and segmental kinetics by cardiac gamma-angiography after revascularization. 18 patients (11 anterior MI, 7 lateral or inferior MI) and 162 segments were analysed semiquantitatively. All patients with persistent significant stenosis underwent secondary revascularization of the artery responsible for myocardial infarction. The prevalence of viability was high, as only 34% of segments initially presented a segmental kinetic abnormality and contraction was improved at 6 months in 54% of cases. Stress scintigraphy and dobutamine echocardiography detected viability with a sensitivity of 96% and 70%, a specificity of 88% and 82%, a positive predictive value of 89% and 77% and a negative predictive value of 95% and 76%, respectively. Only the wall score index with low-dose dobutamine was correlated with the ejection fraction at 6 months. Stress echocardiography is a more reliable predictor of the degree of functional recovery after revascularization. Scintigraphy visualizes much more extensive abnormalities than echocardiography. This often corresponds to ischaemic territories with normal contraction under baseline conditions and low doses of dobutamine. It therefore seems preferable both examinations for optimal assessment of thrombolized patients following myocardial infarction.

A comparison of low- with high-osmolality contrast agents in cardiac angiography. Identification of criteria for selective use.

BACKGROUND: Controversy exists as to whether low-osmolality radiographic contrast agents, which have less detrimental pharmacological effects but are considerably more expensive than high-osmolality agents, should be used universally or only for selected high-risk patients. METHODS AND RESULTS: A randomized, double-blind study was used to compare the frequency and severity of adverse events in 2245 consecutive patients undergoing diagnostic cardiac angiography. Two thousand one hundred sixty-six patients were successfully randomized to either iohexol, a low-osmolality contrast agent, or diatrizoate (as Hypaque 76), a high-osmolality agent. The end point event included clinically important adverse events (which jeopardized the patient or required aggressive treatment), contrast agent-related procedure abbreviations, and conversion to open-label contrast agent. Clinically important end point events were associated with increased age, New York Heart Association functional class, left ventricular end-diastolic pressure, arteriovenous oxygen difference, severity of coronary artery disease, and history of a previous reaction to contrast agent. End point events were less frequent in patients receiving iohexol (2.6% versus 4.6%; adjusted odds ratio, 1.59; 95% confidence interval, 0.97-2.60; P = .07). The difference in event frequency between iohexol and diatrizoate was confined to the highest-risk quartile of the patient population. An algorithm was developed to classify patients as being at high or low risk for an event based on patient age, New York Heart Association class, history of a prior contrast reaction, and left ventricular end-diastolic pressure. Application of this algorithm for selective use of low-osmolality agents only for high-risk patients to a theoretical population of 1000 patients reduced contrast agent costs 66% without increasing the frequency of contrast agent-related adverse events. CONCLUSIONS: The advantages of low-osmolality contrast agents are clinically important in patients with severe heart disease but are not in less ill patients. Universal use of low-osmolality agents for cardiac angiography in an unselected population is not necessary. Appropriately guided selective use of low-osmolality contrast agents is feasible and has the potential to reduce cost substantially without compromising safety or effectiveness.

Surgical treatment in tetralogy of Fallot diagnosed by echocardiography.

The purpose of this paper is to present the authors' 3-yr experience of echocardiographic examination of patients with the clinical diagnosis of tetralogy of Fallot, and their evaluation for surgical treatment without prior cardiac catheterization. Among the patients with the clinical diagnosis of tetralogy of Fallot 227 had a definite diagnosis made by M-mode, two-dimensional, Doppler and contrast echocardiography. For the diagnosis of tetralogy of Fallot, ventricular septal defect, pulmonary stenosis, and overriding of the aorta were considered to be fundamental. Ventricular septal defect could be seen easily in the subaortic region by two-dimensional echocardiography. However, in some patients whose ventricular septal defect was not seen clearly, peripheral vein contrast echocardiography was performed. The diameters of pulmonary artery, and main branches at a few millimeters distal to their origin were measured. These parameters were correlated with the aortic diameter for evaluation as to whether they were able to accept the total cardiac output. In patients whose left ventricular end-diastolic dimension was small, shunt operation was preferred. In 115 patients the pediatric cardiologist performing the echocardiography thought that cardiac catheterization was necessary. In these cases the reliability of echocardiography in detecting important cardiac abnormalities was evaluated. Detection of ventricular septal defect, presence of pulmonary valve, detection of stenosis on the pulmonary bifurcation and/or main branches revealed a high sensitivity. Two-hundred-and-one patients diagnosed by echocardiography underwent total correction. In all cases except one the preoperative diagnosis was confirmed by surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of iohexol and diatrizoate-meglumine in children undergoing cardiac catheterization.

Iohexol (Omnipaque) and meglumine and sodium diatrizoate (Renografin-76) were compared in a double-blind, randomized study for their efficacy, safety, and hemodynamic effects as angiographic contrast agents in children. Forty-four children were randomly allocated to receive either iohexol or diatrizoate as a component of their routine or emergency cardiovascular evaluation. Following age stratification, baseline physiologic parameters were not significantly different between patients receiving either iohexol or diatrizoate. After systemic ventricular injection, iohexol produced significantly less hemodynamic alteration in systemic systolic blood pressure, systemic ventricular end-diastolic pressure, and dP/dt. Less alteration in heart rate and significantly less effect on the QT interval were seen with iohexol. Image quality was comparable, although significantly more patient mobility was associated with diatrizoate-meglumine. This study shows that iohexol, a nonionic contrast medium, causes less hemodynamic disturbance than diatrizoate-meglumine in children. Therefore, its use to be preferred in these potentially high-risk patients.

Comparison of left coronary and laevo-phase pulmonary angiograms in detecting left atrial thrombi in rheumatic mitral stenosis.

We have compared the diagnostic accuracy of left coronary and laevo-phase pulmonary angiograms in detecting left atrial thrombi in 27 consecutive patients with rheumatic mitral stenosis who underwent both these procedures prior to open-heart surgery. In 10 patients, both procedures were 'positive' for thrombus, confirmed at subsequent surgery in all instances (true positive). Both procedures were negative for thrombus in 11 patients, and none of these patients showed thrombi at subsequent surgery (true negative). Left coronary angiography only was positive for thrombus in one patient in whom no thrombus was found at surgery. Laevo-phase pulmonary angiography only was positive for thrombus in five patients, two of whom had thrombus at subsequent surgery. The sensitivity, specificity and predictive accuracy of left coronary angiogram were 83.3% and 93.3% and 90.9% and that of laevo-phase pulmonary angiogram 100%, 80% and 80% respectively. Laevo-phase pulmonary angiograms showed higher sensitivity and left coronary angiograms showed higher specificity for angiographic diagnosis. However, the differences were found to be statistically insignificant. Angiography is a reliable method for detecting left atrial thrombi if both left coronary and pulmonary angiograms are performed and both procedures are positive or negative for thrombus.

Reproducibility of ventricular function measurements by contrast angiography.

Interobserver reproducibility of single plane contrast angiographic measurements of end-diastolic volume (EDV/m2), end-systolic volume (ESV/m2), stroke volume (SV/m2), and ejection fraction (EF) was studied in two groups of patients. The first group (n = 42) was an unselected, consecutive series of patients in which the calculations of volume were performed manually, representing day-to-day results from a clinical quantitative angiographic laboratory. The second group (n = 31) was selected on the basis of optimal filming technique and volume calculations were performed digitally with the aid of a computer. This group characterizes the reproducibility that could be attained for investigational purposes. In the selected group, interobserver reproducibility of four regional ejection fractions was determined. The correlation coefficient (r), standard error of the estimate (Sy.x), average difference, and 95% confidence limits are given. Measurement variation accounted for 9-15% of the variance in this study for EDV/m2 (consecutive series), indicating that caution is needed when relating contrast angiographic measurements to other (e.g., noninvasive) measures of volume by simple linear regression.

Effect of filming projection and interobserver variability on angiographic biplane left ventricular volume determination.

Although biplane right anterior oblique-left anterior oblique (RAO/LAO) quantitative left ventricular (LV) angiography is commonly performed, justification of LV volume calculation using the area length method (originally formulated from anteroposterior-lateral (AP/LAT) angiograms) has been limited. To assess whether RAO/LAO and AP/LAT LV volumes are similar when computed by the area length method formula, we performed biplane cine LV angiography in both RAO/LAO and AP/LAT projections in random sequence in 21 patients and four LV models of known volume. LV silhouettes were drawn independently by two trained observers. Calculated angiographic volume of the models correlated almost exactly with their true volume (r = 0.999), establishing the absolute accuracy of this system. Rotation of the LV models through 90 degrees of obliquity at 10 degree increments demonstrated a mean change from true volume of only -5.4 +/- 0.7% (p less than 0.001). In the patient studies, rotation to the 30 degree RAO/60 degree LAO position was associated with significant changes in magnitude of biplane areas and long axes, but area length volume estimates were unchanged. Excellent correlation was found between area length calculated AP/LAT and RAO/LAO volumes with r = 0.90, 0.97, and 0.91 for end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF), respectively. Furthermore, interobserver agreement in volume assessment was excellent, with r = 0.98, 0.99, and 0.94 between observers for EDV, ESV, and EF, respectively. Interobserver and inter-method variability for estimates of LV volume and EF ranged from 5--10%. We conclude that when using RAO/LAO LV angiography, volume calculation by the area length method is justified.